Standard pin and sleeve devices typically are comprised of a male plug having “pins” and a female connector or receptacle (connected to a power source) having mating sleeve-like contacts (“sleeves”). Some form of plug-to-receptacle latching usually is provided at least to prevent accidental separation of those components. The electrical connection is made through the mechanical insertion of the plug pins into the receptacle sleeves.
For safety reasons, the receptacle's sleeves must not be energized or accessible unless a mating plug is properly and fully inserted. Several types of arrangements afford such protection:                Type I: These devices employ an apertured, plug-displaceable safety disc that covers the “live” sleeves when no plug is present.        Type II: In these devices the sleeves are internally switched with respective “live” inner contacts and are kept open when no plug is present to automatically provide an exposed “dead face” (see, e.g., U.S. Pat. Nos. 4,659,160 and 4,488,765).        Type III: These devices add to the Type II arrangement an external actuator for manually closing and opening the internal (sleeve and inner) switch contacts only when the plug and the receptacle are joined and for preventing their separation when the switch contacts are closed (see, e.g., U.S. Pat. Nos. 4,140,358 and 4,678,254).        